1. Field of the Invention
The present invention generally relates to a padlock, particularly to a dual-operational padlock which can be operated by either a key or a combination.
2. Description of the Related Art
A padlock is a well known product and is applicable to a variety of articles which may be under an obvious or potential safety risk, to prevent them from being opened. For example, to prevent an unintended user from opening a luggage, a padlock can be used to lock the overlapped pull tabs of the zipper of the luggage such that the zipper cannot be separated.
Generally, based on the locking mechanism utilized, conventional padlocks can be divided into two groups, key-operated padlocks and combination-operated padlocks. These two groups of padlocks have their respective advantages: namely, the key-operated padlock avoids the risk that a combination is forgotten; and the combination-operated padlock does not need a key and thus avoids the risk of losing it.
Yang's U.S. Pat. No. 6,539,761, discloses a padlock combining the functions of a key padlock and a combination padlock. A user thus is able to use either a key or a combination to unlock the padlock. In this case, both locking operations are performed to lock a shackle, and both ends of the shackle are extended into a casing of the padlock and restricted therein. Accordingly, when the padlock is in a locked state, the article hooked by the shackle and restricted by the casing and the shackle cannot be taken off; and when the padlock is in an unlocked state, the shackle axially moves with respect to the casing, and one end of the shackle separates from the casing to form an opening to release the hooked article.
According to the disclosure of U.S. Pat. No. 6,539,761 as well as the related prior art, to lock the shackle, the shackle generally has a notch formed thereon for engaging with the locking mechanism associated with the shackle; that is, the notch plays a key role in letting the locking mechanism lock the shackle. The disadvantages resulted therefrom are that the forming of the notch on the shackle needs more machining processes and decreases the structure strength of the shackle.